feat: implement waterfall layout with smart image positioning and infinite scroll

- Add single-column layout for homepage articles
- Implement smart image positioning based on aspect ratio:
  * Landscape images (ratio > 1.2) displayed on top
  * Portrait/square images (ratio ≤ 1.2) displayed on left side
- Add infinite scroll with lazy loading
- Create new API endpoint /api/articles for pagination
- Add loading indicator and 'no more articles' message
- Optimize performance with image lazy loading and scroll throttling
- Add responsive layout for mobile devices

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

handlers/home.go

@@ -1,6 +1,7 @@
 package handlers
 
 import (
+	"fmt"
 	"net/http"
 	"time"
 
@@ -33,6 +34,39 @@ func HomePage(db *gorm.DB) gin.HandlerFunc {
 	}
 }
 
+// HomeArticlesAPI returns articles in JSON format for infinite scroll.
+func HomeArticlesAPI(db *gorm.DB) gin.HandlerFunc {
+	return func(c *gin.Context) {
+		page := 1
+		if p, ok := c.GetQuery("page"); ok {
+			var parsed int
+			if _, err := fmt.Sscanf(p, "%d", &parsed); err == nil && parsed > 0 {
+				page = parsed
+			}
+		}
+
+		pageSize := 10
+		offset := (page - 1) * pageSize
+
+		var articles []models.Article
+		db.Where("status = ?", models.ArticlePublished).
+			Order(publishedArticleOrder).
+			Limit(pageSize).
+			Offset(offset).
+			Find(&articles)
+
+		var total int64
+		db.Model(&models.Article{}).
+			Where("status = ?", models.ArticlePublished).
+			Count(&total)
+
+		c.JSON(http.StatusOK, gin.H{
+			"articles": articles,
+			"hasMore":  int64(offset+len(articles)) < total,
+		})
+	}
+}
+
 // ArticleDetail renders a single published article by its slug.
 func ArticleDetail(db *gorm.DB) gin.HandlerFunc {
 	return func(c *gin.Context) {